This page was created by Jonas Pfeiffer.
I'm fascinated with aircraft accidents. The reasons and and intricacies of what exactly happens are very interesting to me. CAT mentions the Lauda Air Flight 004 crash, but there are a striking number of other accidents which illustrate some of the problems covered in FR very well or come close to recreating certain scenarios in real live. I'd like to take this opportunity to introduce you to some of them. The first of these is China Airlines Flight 006.
China Airlines flight 006 is arguably very close to being a real live version of the Airbus A380 plummeting to earth in task 10 of chapter 8.
The flight was conducted using a Boeing 747SP (Special Performance not space plane here). The flight was scheduled to fly from Taipei to Los Angeles on February 19, 1985.
As you can see, the airplane descended 30,000 feet (9,100 m) in under two in a half minutes and
endured a
maximum acceleration of 5.1 g.
The incident was attributed to:
"The captain’s preoccupation with an inflight malfunction and his failure to monitor properly the
airplane’s
flight instruments which resulted in his losing control of the airplane. Contributing to the
accident was
the captain’s over-reliance on the autopilot after the loss of thrust on the no. 4 engine." (NTSB
report)
After the outer right engine failed, the autopilot reached its aileron deflection limit. The
captain then
disengaged the autopilot and the plane rolled until it reached an extreme nose down attitude.
The pilot only managed to regain control after exiting the clouds.
The aircraft was significantly damaged in the incident and there were two serious injuries.
For the very interested, the National Transportation Safety Board (NTSB) report of the incident is available here.
Another flight which plummeted towards earth is Alaska Air 261, but unlike the last example, this flight involving a McDonnell Douglas MD-83 did crash.
Flight 261 departed Puerto Vallarta en route to San Francisco on January 31, 2000. Approximately 100 minutes into the flight, the crew experienced control problems and contacted air traffic control. Eventually the nut of the elevator trim jackscrew mechanism failed causing the plane to pitch down into the sea. All of the 88 people on-board perished.
Once again, the National Transportation Safety Board (NTSB) report is available here.
After our last example of a failed horizontal stabilizer, we will now have a look at the failure of a
vertical stabilizer.
American Airlines Flight 587 was meant to fly from New York to Santo Domingo on November 12, 2001 using an
Airbus A300.
The flight departed John F.
Kennedy Airport at 09:12 EST.
At 09:15 the aircraft encountered wake turbulence
from a JAL Boeing 747-400, which led the First Officer to alternate left and right rudder
deflections.
The resulting and alternating sideslip caused the vertical stabilizer to detach from the airplane.
A flat spin ensued which ended when Flight 587 impacted
Queens killing all 260 occupants
instantly.
This accidents highlights another reason why it is mandated to use rate limiters for control surface
deflection in task 1 of chapter 4.
It may also be sensible to limit the maximum control surface deflection depending on flight
conditions. As
the NTSB
report
notes:
"The in-flight separation of the vertical stabilizer as a result of the loads beyond ultimate design
that
were created by the first officer’s unnecessary and excessive rudder pedal inputs. Contributing to
these
rudder pedal inputs were characteristics of the A300-600 rudder system design and elements of the
American
Airlines Advanced Aircraft Maneuvering Program."
While the First Officer was attributed the blame, Airbus and American Airlines were also declared to be
partially responsible.
Occurring just two months after the 9/11 attacks, this accident hit New York deeply. It also
reinforced
stereotypes against Airbus made planes in the US.
As referenced in task 6 in chapter 6, Lauda Air flight 004 crashed because the thrust reverser in
the left-hand engine deployed in flight.
The flight, which was conducted using a Boeing
767-300ER, was scheduled to fly from Bangkok,
Thailand to Vienna, Austria on May 26, 1991.
After taking off at 23:02 local time, the crew received a warning indicating a problem with the
number one engine thrust reverser at 23:08.
This led the crew to consult the aircraft's handbook. They concluded that no urgent action was
necessary and nothing dangerous had happened.
At 23:17 the number one engine thrust reverser deployed. The aircraft then entered an irrecoverable
diving turn and crashed, killing all 223 on-board.
In the aftermath of the crash a dispute between Boeing, the manufacturer of the plane, and Niki
Lauda, owner and CEO of Lauda Air and former Formula 1 world champion, ensued.
The two parties disagreed who was to blame. The cause of the thrust reverser deployment has never
been identified, but nevertheless eventually Boeing issued a statement that the accident was not
survivable.
Thus the blame lay with Boeing and neither Lauda Air (operator) nor Pratt and Whitney (engine
supplier) could have prevented the accident.
The full Thai accident report can be found here.
As mentioned in the lecture
notes (page 106), a plane crashed on approach to John F. Kennedy International airport on
June 24, 1975.
The plane mentioned was Eastern Air Lines Flight 66 operated by a Boeing 727. Flight 66 was
scheduled from Louis Armstrong New Orleans International Airport to New York and departed New
Orleans at 13:19 EDT.
The flight proceeded as planned until the aircraft approached its destination. A severe
thunderstorm closed in on the airport. Nevertheless the plane was cleared to initiate a landing on
runway 22L and proceeded with a normal approach.
At 16:05 the aircraft entered a downburst caused by the thunderstorm
and descended until it struck
approach lights.
Of the 124 aboard only 11 survived the accident.
Upon investigation by the NTSB it was found that another Eastern Airlines Flight, which landed three
slots before Flight 66 attempted to do so, almost
crashed as well.
According to the Cockpit Voice Recorder (CVR), the captain of Flight 66 was aware of the wind shears, but
decided
to attempt to land anyway.
The probable cause according to the NTSB report
was:
"The aircraft's encounter with adverse winds associated with a very strong thunderstorm located
astride the ILS localizer course, which resulted in high descent rate into the non-frangible
approach light towers.
The flight crew's delayed recognition and correction of the high descent rate were probably
associated with their reliance upon visual cues rather than on flight instrument reference.
However, the adverse winds might have been too severe for a successful approach and landing even had
they relied upon and responded rapidly to the indications of the flight instruments.
Contributing to the accident was the continued use of runway 22L when it should have become evident
to both air traffic control personnel and the flight crew that a severe weather hazard existed along
the approach path."
It is also interesting, that the NTSB reported 12 survivors although one of these died nine days
later. This person was classified as a non-fatal injury as he died more than seven days after the
accident, which was at that time the cut-off date for fatalities.
This has since been increased to 30 days.
BOAC Flight 911 was scheduled to fly from Tokyo to Hong Kong on March 5, 1966. This Route was part of a
service from San Francisco to Hong Kong.
Flight 911, operated by a Boeing 707, took off at
13:58 local time and climbed close to mount Fuji when it began to trail white smoke and lost altitude
suddenly.
Following this, the aircraft began to disintegrate before finally the forward fuselage broke off at
approximately 2000 m of altitude.
Of the 124 occupants, none survived.
According to ASN the probable
cause of the accident was:
"The aircraft suddenly encountered abnormally severe turbulence over Gotemba City which imposed a gust load
considerably in excess of the design limit."
This accident is significant, because it marks one of the very few times were the crash and even
disintegration of an airliner was attributed to turbulence.
The proximity of mount Fuji, highest mountain and
cultural icon of Japan, may have played a role in the accident (see lee wave).
In the course of the accident investigation stress cracking of the vertical stabilizer bolt holes was found,
but ruled out as a cause of the accident. As this was a serious safety issue, maintenance of all Boeing
707s and 720s was corrected to reduce safety risks.
Delta Air Lines Flight 191 was a US domestic flight from Fort Lauderdale to Los Angeles with a stop-over at Dallas/Fort Worth on August 2, 1985. It was conducted by a trijet Lockheed L-1011 Tristar. The Tristar departed Fort Lauderdale at 14:10 CDT.
When Flight 191 approached the destination airport, thunderstorms had moved in. As the aircraft type was able to land using an instrument landing system (ILS), the crew decided to do so. After being cleared to land by air traffic control (ATC), Flight 911 encountered microburst induced wind-shears, causing the plane to strike a plowed field short of the runway. At this point the aircraft remained structurally intact, but contact with lighting equipment of Highway 114 and a car (the occupant of which was killed) led to the aircraft disintegrating. The remains of the Tristar only came to a rest when the plane hit a water tank, having by now skidded onto airport property. Of the 163 occupants, 136 died and 25 were injured.
As with Eastern Air lines Flight 66, a microburst/wind shear phenomenon was at least partially to blame in
the accident.
Probable cause from the NTSB report:
"The flight crew's decision to initiate and continue the approach into a cumulonimbus cloud which they
observed to contain visible lightning; the lack of specific guidelines, procedures and training for avoiding
and escaping from low-level wind shear; and the lack of definitive, real-time wind shear hazard information.
This resulted in the aircraft's encounter at low altitude with a microburst-induced, severe wind shear from
a rapidly developing thunderstorm located on the final approach course."
The crash emphasized the danger of wind shears. At the time of the accident, there were no on-board warning systems to detect these. In the aftermath of the accident such a warning system was tested by NASA and it has since become mandatory for commercial aircraft in the USA to have on-board wind shear warning systems.
This picture was taken at Pima Air & Space Museum in Tucson, AZ in 2018. Pima is one of the biggest air and space museums in the world and features favorable storing conditions and a lot of space. It is also located close to the biggest aircraft boneyard in the world. The space depicted here however is not part of the boneyard, but rather a working area of the museum.